Process of impregnating wood.



c. ks. SMITH.

PROESS 0F IMPBEGNATING WOOD. APPLICATION FILED JN.11,1911. 992,918, Patented May 23,1911.

17H/Ew] UNITED STATES PATENT OFFICE.

CHARLES S'llnlllell'al'i SMITH, OF BERKELEY, CALIFORNIA.

PROCESS OF IMPREGNATING WOOD.

Specification of Letters"Patent. Patented lusty-@ 19m-f, Win-f: "gg-fama? Application led January 11, 1911. Serial No. 602,121. (DEDICATED T THE PUBLIC.)

'of Marche, 188e, chapter 14e (22 stat., 625),

and the inventlon herein described and claimed may be used by the Government of the' United States or any of its officers or employees, or any person in the United States, without payment to me of any royalty thereon.

The object of this invention is to enable opengrained timbers, especially railroadties, to be impregnated with creosote or other preservative substances tothe desired depth and at the same time reduce the cost of such treatment.,

'My invention will be more readily understood by the following description, read in .connectlon with the accompanying drawing which illustrates the method by which my invention may be practiced:

In describing my process, I shall especially refer to the treatment of railroad ties, but it will be understood that green or partly seasoned or driedv timber generally may be treated in a similar manner.

The drawing shows an elevation of a suit- -able apparatusfor carrying out my process.

The ties, etc., are run into the retort or cylinder 1, preferably on car's or trucks, not shown, and thereupon the doors of the c linder are closed to make the latter air tlght. Liquid,'e. g., creosote, crude oil, asphalt or other liquld having a boiling polnt considerably above that of water 1s then introduced from this storage tank/2 byo enin valves 3 and 13. This liquid is then IlJieate by admitting steam to the coils 5, to a temperature sliglhtliy above the boilin point of water, 220 aving been foun to be a suitable tem erature.v The heat is maintained for su cient time to drive out most ofthe' water and 'sap contained in the wood, one to two hours generally being sutlicient. The evaporated water, sap, and any of the oil carried over are condensed in the condenser 6 and flow into the vessel 7 from whence tbey'can be drawn olf for subsequent pirlrification and use, as may be desired. ien most of the water has been driven vfrom the wood, the oil is withdrawn from' the retort 1 tobthe'tank 8,'by opening valve 9. Air under pressure then enters retort 1 60 from air pump 10 until an'air ressure of 50 lbs. per square inch is obtaine) within the retorty which pressure is maintained until the pores of the wood are filled with airat The time necessubstantially that pressure. sary varies with the condition of the wood at this stage, one hour, more or less, gen-O erally being sutiicient. Steam isthen shut oil' from the colls 5. During this time or laterv the oil is pumped u from tank 8 to 70 the tank 2, to leave the tan c 8 empty. Creosote oil, or other preservative liquid, at a temperature of about 120 F. from the tank 4 (provided with a ge board) is then pumped into the. cylin er (Without any reuction of thel air pressure) by the pumfp 12, to fill the cylinder, and the action o the pump continued until the pressure of the oil is raised to 157 pounds within the retort until any desired amount of absorption is secured. The oil remaining in the cylinder 1 which has not been taken up by the'wood is then allowed to Howl into the .receiving tank 8, by opening the valve 9. The compressed airwithin the cells of the wood, then expands to drive out a large amount of the oil taken up by the wood, which also runs into the tank 8. A vacuum may then be applied, if desir'ed, Vwhich will have the efect of removing a further quantity of the preservative oil from the wood. This may be done by changing the valves in the pipes 11 leading to the air pump, so that this will work as a vacuum pump.

The relatively cold preservative (120 de- 95 grees F.) assisted by the second pressure 157 ounds) when it comes in contact-with t e re atively hot woodLwill cause a partial .contraction of the com ressed air contained is and readily and 100 thoroughly fill the cells to a depth deter-E withinl the, Wood cel mined an equalization of the contained and app ied pressure. Upon the release of the pressure the free preservative contained within the wood cells will be expelled with the exception of a small amount which adheres to the cell 'walls This actonhcan be assisted by the ap lication of a vacuum. Cresote is preferre as a reservative, although other oils and soluli) le salts may be used. By the addition of a lowering of temerature tothe increase in pressure, muchv ower pressures need be utilized to obtain equal results. For example: A change in.

temperature 100 degrees F. (from 220 degrees to 120 degrees) will in itself result in a 2O per cent. reduction ofvolume. This correslponds to 43 pounds pressure. `Consequent y a pressure of 153 pounds accompanied by a drop of 100 degrees in temperature will give the same resu t as a 200 pound pressure without the temperature change. At the completion of the process there will be absorbed from 4 to 8 vpounds of. preserva- .tive per cubic foot of timber.

By means of my invention I am enabled I to el'ect a saturation of the fibers -to the desired depth, with the use of a comparatively small quantity of preservative, thus reducinglgreatly the cost of wood impregnation.

aving thus described my invention,` I

claim- 1. The herein described process of preserving wood which consists in introducing the wood into an air tightcylinder, subjecting the wood in said lcylinder to the1 action, l

ofthe bath of oil at approximately 220 degrees F. for a length of time suilicient tov heat up the wood and thereby vaporize most of the water contained in the wood, then drawing of the oil and applying anair pressure of about 50 pounds per square inch,`

lntroducing a` preservative oil vat approximately '120 degrees F. andraising thepre'sheat up the wood and thereby vaporize most of the Water contained in the wood, then drawing oii' the oil and applying an air pressure of about 50 pounds per square inch, introducing a preservative oil at approximately 12C degrees F. and raising the pressure tov about 157 pounds per square inch, for al length of time sufficient to insure the desired impregnation, then relieving the pressure and simultaneously drawing off the unabsorbed oil and -then subjecting the wood to a vacuum for` the purpose of drawing out a portion of the oil from the cell cavities. In testimony whereof I have signed this specication in the presence of two subscrib- 1ng witnesses. l

CHARLES STOWELLISMITH.

Witnesses: y

Connu DU Bols, p F. E. OLMs'rED. 

